The invention generally relates to devices for limiting torque to a predetermined torque value, torque limiters, and for preventing transmission of torque from a driven member through its output means to its input means, no-back devices. More particularly, this invention relates to a dual-full function torque limiter/no-back device having a brake section which is utilized to provide both torque limiting and no-back functions.
Single function torque limiters and single function no-back devices which actuate a braking section incorporated in said devices are well known in the art. Furthermore, a "combination no-back brake and torque limiter assembly" utilizing a drive coupling assembly or clutch of the ball-detent type is known in the prior art, namely U.S. Pat. No. 4,176,733. It is used, as in this invention, in various types of actuator for aircraft components, where both functions must be provided and where space and weight limitations are severe requirements. This device is both bi-directional, that is, it operates in the same manner whether the input torque is clockwise or counterclockwise, and bilateral or symmetrical with respect to its "output" torque characteristics. This is to say that its "output" torque characteristics are identical for torque applied through either its designated input or output shafts. Such bilateral device has three phases of operation and they are identical regardless of which shaft the torque is applied. When the input torque is below a first predetermined, minimum torque level, the brake assembly is in pressure engagement and the output torque is maintained at a zero torque level. To be more specific, the brake's pressure engagement is progressively released as the input torque increases until the first predetermined, minimum, torque level is reached at which point the brake is released and is moved to a null position or mid-position where there is no torque resistance due to the brake; prior to such null position being reached, the output torque is at a zero torque level. The null position is reached when the balls of the drive coupling assembly travel to the end of its inner, first, ramp section thereby fully overcoming an axial pre-load of its associated spring. Then the input torque above such first predetermined, minimum, level is freely transmitted to the output shaft. As the input torque level increases toward a second predetermined maximum torque level, these balls move onto an outer second ramp section, and progressively therealong, to increase the spacing between the drive discs of the drive coupling assembly, until the brake assembly is again engaged, albeit in a different manner, when the input torque level reaches this maximum level to limit the torque level at the output shaft.